How to convert respectively four column to date formatting at MATLAB? - matlab

Question

Excel file(104976x10) includes large data.
A column: Time (unit year)
B column: Year
C column: Day of the year
D column: Hour
E column: Minute
and others including values
I would like to convert column which begins with B column until E column to date format like 'dd/mm/yyyy HH:MM'.
Example for the data:
1998,41655251 1998 152 1 0 12,5 12,0 11,8 11,9 12,0
I would like to do date instead of 2-th, 3-th, 4-th and 5-th columns.
1998,41655251 01/06/1998 01:00 12,5 12,0 11,8 11,9 12,0
or
1998,41655251 01/06/1998 01:00 1998 152 1 0 12,5 12,0 11,8 11,9 12,0

Answer 1

Welcome to SO.
Matlab has two types of date-format:
datetime, introduced in 2014b.
datenum, introcuced in long ago (before 2006b), it is basically a double precision value giving the number of days from January 0, 0000.
I think the best way is to use datetime, and give it the year, month, day, hour and minute values like this:
t=datetime(1998,0,152,1,0,0)
t= '01-May-1998 01:00:00'
As you can see the days automatically overflow into the months. But I end up 1st of may, not 1st of june like in your example.
to change the format:
t.Format='dd/MM/yyyy hh:mm'
t= '01/05/1998 01:00'
to convert it to a string, you can simply use string(t)
This is an example that combines the above functions to read an xlsx file and writes a new one with the updated column.
data=xlsread('test.xlsx');
S = size(data);
t = datetime(data(:,2),0,data(:,3),data(:,4),data(:,5),0);
t.Format='dd/MM/yyyy HH:mm';
data2=num2cell(data(:,1));
data2(:,2)=cellstr(string(t));
data2(:,3:S(2)-3)=num2cell(data(:,6:end));
xlswrite('test2.xlsx',data2);